Relative mobility determines the efficacy of MPAs in a two species mixed fishery with conflicting management objectives

Marine Protected Areas (MPAs) have been used to protect species in need of conservation and as a fisheries management tool. It has been suggested MPAs can benefit mobile stocks by protecting spawning grounds whilst also allowing yields to be maintained as mature fish move out of the protected areas. However, the robustness of this claim in mixed species fisheries has yet to be established. We use a simulation model to explore the efficacy of spatial closures and effort regulation when other forms of fishery control (e.g., Total Allowable Catches) are absent or non-enforced as ways of addressing management objectives that are difficult to reconcile due to the contrasting life-histories of a target and a bycatch, conservation species in a two-species fishery. The mobility of each stock in such a fishery affects the benefits conferred by an MPA. The differing management objectives of the two species can be partially met by effort regulations or closures when the species exhibit similar mobility. However, a more mobile conservation species prevents both sets of aims being met by either management tool. We use simulations to explore how spatial closures and effort regulation can be used to seek compromise between stakeholders when the mobility of one stock prevents conflicting management objectives to be fully met. Our results demonstrate that stock mobility is a key factor in considering whether an MPA can meet conflicting aims in a multispecies fishery compromised of stocks with differing life histories and mobilities

Addressing Criticisms of Large-Scale Marine Protected Areas

Designated large-scale marine protected areas (LSMPAs, 100,000 or more square kilometers) constitute over two-thirds of the approximately 6.6% of the ocean and approximately 14.5% of the exclusive economic zones within marine protected areas. Although LSMPAs have received support among scientists and conservation bodies for wilderness protection, regional ecological connectivity, and improving resilience to climate change, there are also concerns. We identified 10 common criticisms of LSMPAs along three themes: (1) placement, governance, and management; (2) political expediency; and (3) social–ecological value and cost. Through critical evaluation of scientific evidence, we discuss the value, achievements, challenges, and potential of LSMPAs in these arenas. We conclude that although some criticisms are valid and need addressing, none pertain exclusively to LSMPAs, and many involve challenges ubiquitous in management. We argue that LSMPAs are an important component of a diversified management portfolio that tempers potential losses, hedges against uncertainty, and enhances the probability of achieving sustainably managed oceans

Evaluation of Dynamic Interactions between Predator, Prey and Fisheries in Ecosystem Models

As fishery production and habitat quality continues to experience declines, there is a growing need to improve the scientific methodologies used to assess and sustain economically and ecologically important fisheries. This requires a sound understanding of the life histories and population dynamics of each species, and development of a robust framework for population modeling. Realization of the multi-species nature of fisheries has prompted a shift towards ecosystem-based approaches to modeling. To evaluate alternative methods for modeling predator-prey interactions within a physically variable coastal-estuarine ecosystem, a food web of national economic and ecological significance comprised of Atlantic menhaden (Brevoortia tyrannus), striped bass (Morone saxatilis), and bluefish (Pomatomus saltatrix) is considered in this study. Understanding the dynamics of biological communities such as this is challenging and requires the formulation of realistic mathematical models. This should be a stepwise process in which the underlying assumptions, parameter sensitivities, and fundamental behaviors of interacting species dynamics described by relatively simple to more complex models are delineated and quantified. In this study two alternative multispecies modeling frameworks were utilized to evaluate the dynamic interactions between predator and prey populations, and to understand the influence of fisheries and environmental temperature change on predator-prey and food chain communities. First, relatively simple, age-independent, predator-prey and food chain models representing generalized, ecological-scale interactions between different trophic groups were developed and analyzed. Sensitivity analyses revealed the relative importance of model parameters and the effect of varying levels of fishing mortality on model dynamics. Overall, the predator-prey and food chain models were shown to be a valuable tool for understanding general patterns in the dynamic behavior of interacting populations. Next, an environment-dependent, age-structured, Atlantic coast spatial dynamic multispecies model was investigated. This more complex model links individual-scale bioenergetic processes controlling growth to ecological-scale rates of natural and predation mortality. Simulations were performed using recent stock assessment estimates of fishery condition and stock sizes to evaluate the nature and magnitude of linkages among menhaden and their key predators, specifically bluefish. This ecosystem model was demonstrated to provide valuable insights into the dynamics of menhaden and bluefish given the underlying dynamics and forcing in the Atlantic States fishery coastal ocean ecosystem. Additionally, the influence of environmental temperature on both modeling frameworks was investigated. This iterative process of model development and analysis advances the current understanding of the species and ecosystem of interest, and ultimately provides an improved basis for multispecies fisheries assessments

Oil And Fisheries In The Gulf of Mexico

The explosion of the Deepwater Horizon offshore drilling rig on April 20, 2010 initiated the world’s largest known oil spill in the Gulf of Mexico Large Marine Ecosystem (LME). Characterized by an extensive continental shelf and substantial nutrient input from rivers and Loop Current-induced upwelling, this region is valued for its high productivity and lucrative fisheries. According to the United States National Marine Fisheries Service, approximately 18% of the U.S. domestic commercial fisheries landings reported in 2009 originated in the Gulf of Mexico. Estimates of the quantity of oil, natural gas and associated methane, and chemical dispersants released as a result of this calamity have been plagued by uncertainty. The U.S. Government-appointed team of scientists, the Flow Rate Technical Group, estimated that a total of 4.9 million barrels of oil were released from BP’s Macondo well, while the results of an independent study suggest that between 4.16 and 6.24 million barrels leaked from the well. Additionally, according to BP’s records, approximately 1.8 million gallons of dispersant were applied at the site of the leak as well as the sea surface. Complex oceanographic processes have made it difficult to determine the current and future distribution of these substances from the surface to the sea floor and their persistence in the marine environment. Most importantly, there is no immediate answer to questions concerning short-term and long-term impacts on habitats and marine organisms in the path of this disaster. The capacity of habitats and species to recover from the effects of oil, methane, and dispersants may have already been compromised due to pre-existing sources of stress. Since the 1950s, heavy fertilizer use within the Mississippi River drainage basin, encompassing 41% of the contiguous United States, has led to increased nitrate loading in the northern Gulf of Mexico. This nutrient-laden, freshwater discharge ultimately results in the formation of periodic, oxygen-depleted “dead zones” devoid of fish, shrimp, and most other invertebrates in shelf waters off the coasts of Mississippi, Louisiana, and eastern Texas. Also, the extensive shrimp trawl fishery in the Gulf of Mexico directly impacts many species of fish and invertebrates due to habitat destruction and bycatch mortality. This uncertainty is particularly troubling for commercial fisheries. While it is difficult to predict the impacts of an oil spill of this magnitude on the future of fisheries in the region, we can infer possible effects by investigating broader patterns. This study presents an analysis of the prespill spatial distribution of commercial fisheries catch and landed value in the Gulf of Mexico LME relative to the post-spill fisheries closure in an effort to evaluate potential economic losses

Understanding the cost of establishing marine protected areas

While the recurrent cost of managing marine protected areas (MPAs) has been documented and estimated, there has been virtually no attempt to quantify the cost of establishing MPAs in the first place. This lack of attention is likely the result of the complexity of the process, involving often uncoordinated efforts of a multitude of governmental and non-governmental entities over a protracted period of time with no clear start and end-point. Using information gathered from a representative subset of MPAs worldwide, this paper presents the first attempt to identify and describe the various components, and explore potential predictors of the total funds spent in the course of establishment. The thirteen MPAs studied vary in size (from 360,000 km2), location (including near- and offshore in both developed and developing countries), objectives and degree of protection. Variation in MPA start-up costs is shown to be most significantly related to both MPA size and the duration of the establishment phase. Development of a method to estimate the potential cost of establishing proposed MPAs should play a crucial role in the conservation planning process.Marine protected area (MPA) Reserve Cost Establishment Conservation Management